1. Field of the Invention
This invention relates to a video tape recorder (VTR) in which video signals are transmitted to, and from a magnetic head.
2. Description of the Prior Art:
A magnetic head is mounted on a rotary drum in a helical scan type VTR. Accordingly, video signals are transmitted through a rotary transformer to, and from the magnetic head. FIG. 1 shows one example 1 of rotary transformers. In the rotary transformer 1, a rotary core 3 is arranged around a stationary core 2. Plural grooves 4 and 5 are formed in the cores 2 and 3, respectively, facing to each other. Coils 6 and 7 are mounted in the grooves 4 and 5, respectively. The rotary core 3 is fixed on the rotary drum (not shown), and rotates therewith. The coils 7 are connected to the magnetic heads which are mounted on the rotary drum. The coils 6 mounted in the stationary core 2 are selectively connected through a change-over switch to a recording circuit and a reproducing circuit in the VTR.
Thus, the video signals are transmitted through magnetic coupling to and from the magnetic heads in the conventional VTR. Accordingly, the conventional VTR has the following defects:
(1) When signals of plural channels are transmitted, distances between the coils 6, and the coils 7 should be so enlarged as to avoid cross talks between the channels. Accordingly, it is very difficult to increase the number of the channels for a definite rotary transformer.
(2) The high frequency characteristic is limited by parasitic capacitance and geometrical size of the rotary transformer. It is difficult to transmit high speed digital signals and broad band signals.
(3) Since the rotary transformer has a resonance characteristic, the impedance matching is limited. There is little freedom of design. Even when the resonant frequency is so designed as to be beyond the band of signals to be transmitted, the signals to, and from the magnetic head have a frequency characteristic influenced by the resonant frequency. When the frequency characteristic is not equalized, and the impedance matching is not obtained, the noise factor S/N is deteriorated.